It is rather rare these days. I blame Steve Jobs: The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently -- Nietzsche

The system doesn't go poof after 30 days of evaluation indeed. That is Microsoft behavior... still, the only reason Red Hat is proprietary is trademarks, and that is logical, because they must be defended for brand recognition. For the rest RHEL is completely open source. Even proprietary software Red Hat bought such as Netscape LDAP and GFS is open sourced. IMO Red Hat are good open source netizens. Heck, probably even good free software netizens. But again, you cannot compare them to Nokia, because they derive profit from different means.